Digital processing and presentation of information is now in wide spread use in the consumer electronics and personal computing industries. Video, audio and text are now digitally manipulated and presented in a variety of applications.
In particular, digital display terminals are fast becoming commonplace—rapidly replacing older analog devices such as cathode ray tube monitors. Digital video transmission may take place between two integrated circuits in a given display device or between two external devices. Device-to-device digital video exchange may be observed between computers and monitors, set-top boxes and television displays, and projectors and display terminals.
To facilitate flexible transmission of digital video data between a transmitting device and a receiver, various standards defining suitable communications are evolving. The current trends use a serial link, to carry one or more data streams.
The DisplayPort standard, for example, provides a high bandwidth (currently 2.7 Gbps per stream), multi-stream forward transmission channel across a data link, with a bit error rate of no more than 10−9 per lane. Each serial stream is referred to as a lane. DisplayPort further provides for a bi-directional auxiliary channel and an interrupt request line from the receiver to the transmitting device, to facilitate link training and the exchange of control data.
Pixels in a digital video frame are sent in parallel using symbols across all lanes. The receiver must be able to identify frames, and to process symbols from different lanes that are transmitted together. As video is transmitted frame by frame, control symbols which carry synchronization information and control commands are required. The information carried by control symbols may include the start and end of vertical and horizontal blanking intervals, commands to reset a scrambler or reestablish a data link, and/or symbols used to synchronize a transmitter to a receiver.
Unfortunately, at such high transmission rates, errors may corrupt the stream and the control symbols which may cause a loss of synchronization between the receiver and transmitter.
The current mechanism for re-synchronizing requires the receiver to alert the transmitter of the loss of synchronization, using the auxiliary channel. However, this may entail an unacceptable delay leading to poor user experience.
Accordingly, there remains a need to for a more robust technique of exchanging control symbols that may be used for re-synchronizing, data delineation or other control.